Method of coating cans



Jan. 19, 1937. J HQTHERSALL 2,067,922

METHOD OF COATING CANS Filed Aug. 2, 1934 2 Sheets-Sheet l fizzy-.1 fi'gf I I I'll I MW Jan. 19, 1937'. J. M. HOTHERSALL 2,067,922

' ME'EHOD 0F COATING CANS I Filed Aug. 2, 1954 2 Sheets-Sheet 2 Patented Jan. 19, 1937 METHOD OF COATING CANS John M. Hothersall, Brooklyn, N. Y., assignor to American Can Company, New York, N. Y., a corporationof New Jersey Application August 2, 1934, Serial No. 738,153

6 Claims.

Another object of the invention is the provision of a method of coating cans which comprises momentarily sealing-an open end of a can above a source of supply of liquid coating material and withdrawing air from the interior of the sealed canv so that the coating material is raised from the source of supply and is caused to flow over the interior can surfaces, the excess of coating material being then returned to the source of supply leaving the interior can walls coated.

A further object of the invention is the provision of a method of liquid coating cans by creating a difference of pressure between the interior of the cans being coated and a source of liquid coating material so that the latter is caused to flow onto the interior surface of the can.

A still further object is the provision of a method of coating cans with a liquid coating material by closing the canto confine an interior space therein into which the liquid coating material is first introduced and then Withdrawn by changing the difference of air pressure between the can interior and the source of coating material.

Numerous other objects and advantages of the Figures 1 and2 are sectional viewsof one form of apparatus for carrying out the method steps of the instant invention, Fig. 1 showing a can in position in the apparatus prior to coating, while Fig. 2 shows the apparatus and can during one of the coating steps; and

Figs. 3 and 4 are similar sectional views of a modified form of coating apparatus which also utilizes the inventive method.

In the method steps of the instant invention either cans having a bottom end or can bodies without ends are momentarily sealed in position on a supporting member associatedwith an open tank which may contain a supply of liquid coating material. In the description and claims that follow when the word can is used it will be understood to refer to either cans having a bottom and/or to can bodies without any ends.

In the sealed position of the can on its tank 5 support the interior of the can is employed as a part of a coating chamber which cooperates with other parts of the supporting member to provide a closed communication between' the can interior and the coating material in the tank. A dif- 1o ference of air pressure is created between the can interior and the surface of the coating material which is outside of the communicating passages connecting with the coating chamber and this is done by drawing a vacuum on the inside of the can and in the chamber. Atmospheric pressure exerting a force on the outside or exposed surfaces of the coating material in the tank then causes the material to rise or flow into the can, completely filling it and covering its inside wall surface.

Atmospheric air is then admitted to the can interior preferably adjacent its top or just above the can andat the same time the vacuum is broken. The liquid coating material within the can immediately drains back into the tank leaving a sufficient portion of it adhering to the desired interior can surface'as a thin even coating.

One form of apparatus for performing the steps of the invention is shown in Figs. 1 and 2 of the drawings and comprises a tank I I having a closed bottom I2 and an open top l3. This constitutes a reservoir for holding a supply of liquid coating material M. A flanged can a to be coated is shown as having both ends open and is supported in the open top of the tank on a central vertical tubular member ll which may be an integral part of the tank structure.

Tubular member I! is open at both ends, having its top end flared out in an angular throat 40 wall l8. The upper surface of the throat wall adjacent its outer edge is recessed to provide a annular channel I9 which carries a. resilient seal- 7 ing ring 21. The bottom flanged end of the can rests on this sealing ring when it is in coating osition.

The bottom end of the member I'I terminates just above the tank bottom I! and is immersed in the coating material in the tank reservoir. Vertical holding webs 23 are preferably the con- 5 necting elements. between the member and the side wall of the tank so that there is free communication between the tank interior and the interior of the member through its lowerend.

The interior of the can is employed as a part of a coating chamber which may be considered to.

also include the interior of the tubular member To provide such a chamber the lower end of the can is momentarily clamped against the sealing ring 2| by a movable head 25. The interior of this head, theinterior of the positioned can and the interior of the tubular member all constitute the coating chamber.

The head 25 is formed with a conical skirt wall 26 which flares out over the top of the clamped can completely covering it. An annular channel 21 is formed in the inside surface of the wall .26 adjacent its outer edge and provides a seat for a resilient sealing ring 28 similar to the ring 2|. The upper flanged end of the can is tightly engaged by the ring 28, the head being brought down on the can in any suitable manner. The joints adjacent both ends of the can are thus hermetically closed or sealed for the duration of the clamp-.

ing period or during the coating operation;

The upper part of the head 25 is hollowed out in a bore 3|, the lower end of which communicates with the top of the coating chamber. The lower end of the bore is closed at times by a ball valve which comprises a float ball 32 held captive by pins 33 threadedly secured in the conical wall 26. These pins support the ball when it is in its lower, non-closing position (Fig. 1).

The surrounding upper wall of the bore is internally threaded and holds a two way hand valve 35. One outlet of this valve is threadedly secured to a pipe 36 which provides a connection with a pump or other suitable source of vacuum. The

' other outlet of, the valve connects with a short vent pipe 31 which is open to the atmosphere.

With the can clamped between the sealing rings 2|, 21, the valve 35 is first turned to open com 4 bular member I1, into the sealed can and on up and into the conical part of the head 25 as shown in Fig. 2.

As the ball 32 floats on the rising liquid it moves up and partially'into the end of the bore 3|. This action closes off the bore and cuts off the vacuum eifect from the coating chamber which at that time is completely fllled with coating liquid (Fig. 2).

The value 35 is now turned to disconnect the head from the vacuum supply and to open communication with the vent pipe 31. Air at atmospheric pressure thereuponrushes into the bore 3| and impinging on the ball 32, opens the coating chamber to atmosphere.

The column of liquid material in the head 25,

can a and tubular member I! recedes under the force of gravity and drops back into the tank, the float ball again seating on the pins 33. In this draining of the liquid out of the can a sufficient amount adheres to the interior can surfaces to provide the desired film or thin, even coating for those surfaces.

In Figs. 3 and 4 of the drawings there is disclosed a slightly different form of apparatus which may be used to carry out the method steps of the invention, this form being particularly adapted for use with cans having attached bottom ends. Such an apparatus comprises a tank 5| which corresponds to the tank previously described. Tank 5| has a bottom 52 andan open top 53 and adapted to be closed by a ball valve.

comprises a float ball 69 which is held captive also functions as a holding reservoir for a coating material 54.

At one end of the tank there is provided a vertical tubular member 56 open at both ends and this member may be an integral part of the tank side wall. The upper end of the tubular member projects above the'top of the tank and is formed with an obliquely disposed angular throat wall 5'! the upper surface of which is preferably inclined at about 30 degrees from horizontal. The can a to be coated is inverted over this throat, the can being provided with a bottom end. The upper surface of the throat wall 51 is grooved in an annular channel 59 which forms a pocket for a resilient sealing ring 6|. The positioned can rests on this sealing ring with its open end sealed or closed from atmosphere.

Tubular member 56 extends down into the tank 5| terminating just short of the bottom wall 52 and is immersed in the coating material. There is therefore free communication between the tank interior and the interior of the tubular member and the latter together'with the interior of the inverted can functions as a coating chamber during the coating operation.

A vertically disposed cylinder 65 is located on the opposite side and is or may be an integral a part of the tank. The upper end of the cylinder extends above the top of the tank and is closed with a cap 66 which is threadedly secured in the top end of the cylinder. The lower end of the cylinder is inside the tank proper, being immersed in the liquid coating material therein. This lower end terminates just short of the tank bottom 52, similarly to the tubular member 56.

The cylinder 65 intermediate its length is formed with an annular web or ledge 61 which has a central aperture or valve seat 68 which is This valve below the aperture, pins ll secured in the web 61 being used for this purpose. This is'an identical construction to the ball valve used to close the bore 3| of the apparatus of Figs. 1 and 2.

The web 61 divides the cylinder 65 into two parts, the upper part being utilized as a vacuum chamber 13. The vacuum chamber is connected to any suitable source of vacuum through a twoway valve H which is threadedly secured at 15 in awall of the cylinder. A pipe 16 extending from the valve is a part of the pipe line leading from the source of vacuum. The other outlet of the valve includes a short pipe 11 the lower end of which is open to the atmosphere.

Vacuum chamber. 13 is connected with the interior'of the can positioned on the sealing ring 6| by a pipe 18. That end of the pipe which extends into the chamber 13 passes through and tightly fits in a hole or aperture 19 formed in the cylinder side wall just above the web 61. The

- other end of the pipe which extends into the tubular member 56 passes through and tightly flts in a hole or aperture 8| formed in the member just below its skirt 51. This end of the pipe is bent as at 82 into the positioned can terminating just short of the can bottom. This terminal pipe end is at the highest point of the pipe (Fig. 3) and is cut off at-an angle to enter the upper corner of the can, this also'being the highest section of the can interior. I

With a can in position on the sealing ring 6| the valve 14 is first turned to open communication between the pipe 16 and the vacuum chamber 13. Air is exhausted from the chamber, from the pipe 18 and from the interior of the posican. sure, the coating material in the can and in the tioned can a. Outside atmosphere surrounding the can only holds it more firmly seated on its resilient ring Bl.

This removal of air from the can and from the vacuum chamber relieves the air pressure on the surface of the coating material within the tubular member 56 and on the surface of the liquid in the lower end of the cylinder 65. Accordingly the coating material rises at these two places being forced up by the atmospheric pressure acting on the surface of the exposedcoating material in the tank.

As the level of liquid in the lower end of the cylinder rises it lifts the fioat ball 69 which guided by the tapered wall surrounding the aperture 68 closes the latter, thereby stopping any further liquid rise in the cylinder.

The rising liquid in the tubular member 56 flows into the can and completely fills it thus covering all of its interior surfaces this being possible by reason of the high position of the end of the pipe I8 within the can as already explained. Some of the coating material flows back and through the pipe 18 and into the vacuum chamber where it falls down on the ball valve. The valve 14 is then turned and the vacuum pull on the vacuum chamber and on the coating chamber is shut off.

Turning of the valve simultaneously opens communication between the chambers and atmosphere by way of the pipe 11 and air at atmospheric pressure immediately enters into the vacuum chamber and into the pipe 18 and thence into the This restores the original balance of prestubular member 56 dropping back to its original level. This action drains the liquid material out of the can, leaving an even coating on all of the required surfaces.

Lowering of the liquid level in the tubular member 56 is accompanied by a like lowering of the liquid level in the cylinder 65 and the ball 69 floats down with the receding liquid and moves away from theaperture 68. This opens the aperture and any of the liquid material drawn over into the chamber I3 passes back into the lower part of the cylinder andinto the tank.

It is thought that the invention and many of its attendant advantages will be understood from the foregoing description, and it will be apparent that various changes may be made in the steps of the process described and their order of accomplishment without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the process hereinbefore described being merely a. preferred embodiment thereof.

I claim:

1. A method of coating cans comprising covering an open end of a can to create a coating chamber which includes the interior of the can, exhausting air from said coating chamber, raisin by atmospheric pressure a liquid coating material from a source of supply to flow into said can and over its interior surfaces automatically cutting off communication between said chamber and the air exhausting source after the former has been filled with the coating material, and restoring the interior of the can to atmospheric pressure to return the excess of coating material to said source of supply leaving the interior can surfaces coated.

2. A method of coating containers comprising closing a container to confine an interior space therein against ingress of atmospheric pressure,

then introducing by atmospheric pressure a liquid coating material from a source of supply spaced from said container into said container interior space, and thence withdrawing it, said introductionand withdrawal being effected by means of differences of air pressures between said container interior space and the source of coatin material.

3. A method of coating containers comprising creating a difference of pressure between the in- 4. A method of coating containers comprising positioning a container to be coated with its interior spaced from and in communication with a confined liquid coating material, and creating a difference of pressure between the interior of said container and the confined coating material so that said material is directed by atmospheric pressure through said container and in contact with its entire interior surface.

5. A method of coating cans comprising placing a can to be coated in an inverted position over and spaced from a liquid coating material, creating a difference of pressure between the interior of said can and the said coating material so that said material is directed and forced by atmospheric pressure into said can, then draining said material out of the can so as to leave a coating on its entire interior surface.

6. A method of coating cans comprising positioning a can to be coated adjacent and spaced from a body of liquid coating material exposed to atmospheric pressure, drawing a vacuum on the interior of said can so that said coating material is forced by atmospheric pressure therein to cover its interior surface, then breaking said vacuum and thereby removing the excess coating material from said can interior at the same time leaving an adhering coating on the can wall.

JOHN M. HOTHERSALL. 

